Revert "version bump gunicorn"

This reverts commit 03c3a1be0bac1454959952886788d0ba4c763ca3. For some
reason, this was causing an import error:

Stacktrace (most recent call last):

  File "raven/middleware.py", line 31, in __call__
    iterable = self.application(environ, start_response)
  File "django/core/handlers/wsgi.py", line 241, in __call__
    response = self.get_response(request)
  File "django/core/handlers/base.py", line 179, in get_response
    response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
  File "django/core/handlers/base.py", line 228, in handle_uncaught_exception
    return callback(request, **param_dict)
  File "django/utils/decorators.py", line 91, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "django/views/defaults.py", line 32, in server_error
    t = loader.get_template(template_name) # You need to create a 500.html template.
  File "django/template/loader.py", line 145, in get_template
    template, origin = find_template(template_name)
  File "django/template/loader.py", line 128, in find_template
    loader = find_template_loader(loader_name)
  File "django/template/loader.py", line 95, in find_template_loader
    mod = import_module(module)
  File "django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/home/picky/.envs/picky/local/lib/python2.7/site-packages/django/template/loaders/app_directories.py", line 23, in <module>
    raise ImproperlyConfigured('ImportError %s: %s' % (app, e.args[0]))

This is worth fixing, but in the meantime I want to ship the current version.